The present invention relates to a paint which is used for waterproofing of rooftop, floor and outer wall of buildings, building materials, sports facilities such as tennis courts and athletic sports stadium, automobiles, household appliances, woodworking products, plastics molded articles, etc. and which can form a paint film excellent in weather resistance, for example, gloss retention, discoloration resistance, and crack resistance in long term outdoor use.
Hitherto, there have been known two-pack curing type paint compositions which comprise a composition containing active hydrogen and a composition having a functional group which reacts with active hydrogen. These paint compositions are excellent in chemical properties such as chemical resistance and, besides, can form a paint film superior in adhesion and strength and have been used as top coats of rooftop of buildings for waterproofing, outer wall of buildings, building materials and sports facilities.
Especially, when an acrylic polyol is used as the composition containing active hydrogen and an isocyanate is used as the functional group which reacts with active hydrogen, a paint film excellent in gloss, chemical properties and mechanical strength can be produced and these paint compositions have been generally used as outdoor paints.
However, when the paint films comprising the above paint compositions are used for a long period of time, they suffer from the problems in weather resistance, such as decrease of gloss, discoloration and cracking due to exposure to ultraviolet rays. For the solution of these problems, an ultraviolet absorber or a light stabilizer is added to the paint compositions. However, when used for a long time, the bleeding phenomenon of the ultraviolet absorber or light stabilizer coming to the surface is caused, and the effects of the additives cannot be retained for a long period of time.
In order to solve the above problems, attempts have been made to fix an ultraviolet absorber or a light stabilizer in the paint compositions. Thus, there has been proposed a method of copolymerizing an ultraviolet absorber or a light stabilizer which comprises an acrylic polyol having a polymerizable skeleton, and paint compositions comprising a polyisocyanate compound and a resin composition obtained by copolymerization of an acrylic polyol with an unsaturated monomer having a hydroxyl group, an unsaturated monomer having a cycloalkyl group, or the like have been reported (JP-A 9 (1997)-3393).
However, according to the above method, if the polyisocyanate compound is inferior in weather resistance or content of the polyisocyanate in the paint composition is high, the whole paint film sometimes deteriorates in weather resistance. Furthermore, in the case of the acrylic polyol of the above composition, dispersibility of pigments is inferior, and when pigment is contained, chalking phenomenon of the paint film occurs after lapse of long term, and the weather resistance cannot be sufficiently retained for a long period of time.